POSIX TIMER- Have multiple timers - c

Question

I am trying to have two timers in my system for two different purpose but I dont understand why it doesnt work. Can somebody help me?Also, Should the handler code be a bare minumum so the tasks themselves dont interfere with the tick? Also can I define separate handler?
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <netinet/in.h>
#include <linux/socket.h>
#include <time.h>
#define SIGTIMER (SIGRTMAX)
#define SIG SIGUSR1
static timer_t tid;
static timer_t tid2;
void SignalHandler(int, siginfo_t*, void* );
timer_t SetTimer(int, int, int);
int main(int argc, char *argv[]) {
struct sigaction sigact;
sigemptyset(&sigact.sa_mask);
sigact.sa_flags = SA_SIGINFO;
sigact.sa_sigaction = SignalHandler;
// set up sigaction to catch signal
if (sigaction(SIGTIMER, &sigact, NULL) == -1) {
perror("sigaction failed");
exit( EXIT_FAILURE );
}
// Establish a handler to catch CTRL+c and use it for exiting.
sigaction(SIGINT, &sigact, NULL);
tid=SetTimer(SIGTIMER, 1000, 1);
struct sigaction sa;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_SIGINFO;
sa.sa_sigaction = SignalHandler;
// set up sigaction to catch signal
if (sigaction(SIG, &sa, NULL) == -1) {
perror("sa failed");
exit( EXIT_FAILURE );
}
// Establish a handler to catch CTRL+c and use it for exiting.
sigaction(SIGINT, &sa, NULL);
tid2=SetTimer(SIG, 1000, 3);
for(;;);
return 0;
}
void SignalHandler(int signo, siginfo_t* info, void* context)
{
if (signo == SIGTIMER) {
printf("Command Caller has ticked\n");
}else if (signo == SIG) {
printf("Data Caller has ticked\n");
} else if (signo == SIGINT) {
timer_delete(tid);
perror("Crtl+c cached!");
exit(1); // exit if CRTL/C is issued
}
}
timer_t SetTimer(int signo, int sec, int mode)
{
static struct sigevent sigev;
static timer_t tid;
static struct itimerspec itval;
static struct itimerspec oitval;
// Create the POSIX timer to generate signo
sigev.sigev_notify = SIGEV_SIGNAL;
sigev.sigev_signo = signo;
sigev.sigev_value.sival_ptr = &tid;
if (timer_create(CLOCK_REALTIME, &sigev, &tid) == 0) {
itval.it_value.tv_sec = sec / 1000;
itval.it_value.tv_nsec = (long)(sec % 1000) * (1000000L);
if (mode == 1) {
itval.it_interval.tv_sec = itval.it_value.tv_sec;
itval.it_interval.tv_nsec = itval.it_value.tv_nsec;
}
else {
itval.it_interval.tv_sec = 0;
itval.it_interval.tv_nsec = 0;
}
if (timer_settime(tid, 0, &itval, &oitval) != 0) {
perror("time_settime error!");
}
}
else {
perror("timer_create error!");
return NULL;
}
return tid;
}

Answer 1

When you define your second timer with this tid2=SetTimer(SIG, 1000, 3);, your code configure this timer to be a one-shot-timer
if (mode == 1) {
itval.it_interval.tv_sec = itval.it_value.tv_sec; // here you arm the timer periodically (that's the meaning of it_interval
itval.it_interval.tv_nsec = itval.it_value.tv_nsec;
}
else {
itval.it_interval.tv_sec = 0; // here you arm the timer once
itval.it_interval.tv_nsec = 0;
}
If you configure the second timer with a mode=1, like this tid2=SetTimer(SIG, 1000, 4);, you'll obtain this on your console :
Command Caller has ticked
Data Caller has ticked
Command Caller has ticked
Data Caller has ticked
Command Caller has ticked
Data Caller has ticked
^CCrtl+c cached!: Success
And you can use different handlers for your timers because you're using different signals to catch their expiration.